We are on leading edge of the space time continuum
How do you view the timeline of the history of life on Earth?
- Starts at early life?
- where is that?
- Is your view biased towards human existence?
- What processes are key? Is tempo (time between events) important?
- Something non-science based?
- Perspective matters: Understanding the history of biodiversity and critical landmarks in life on Earth help us analyze current changes on Earth
The Earth is old…and it took a while for life to form.
- Surface was way too hot to start
- cooled enough to make a solid crust
- cooled enough sustain liquid water
- An atmosphere needed to form
- without an ozone layer, radiation from sun was too intense
- oxygen needed to accumulate for animals
- Lots of inorganic molecules but few organic molecules
- early atmosphere was reducing (oxidation prevented by absence of oxygen)
- organic = compounds of carbon (basic building blocks of life)
Miller & Urey experiments
Miller & Urey experiments
Origin of heredity was key for contempoary life
- RNA (molecule that could replicated itself) probably came first
- ~3.8 billion years ago
- Somewhere between the formation of RNA and cellular life a mechanism to pass genetic information from parent to offspring emerged (heredity)
- Heredity is the key for evolution of life and biodiversity
- replication → variation → competition → natural selection
- mutations (replication mistakes) are the unit of variation
- Heredity likely took place in early ‘protocells’ with compartmentalized RNA
- have not been re-created in the lab
Cellular life begins ~3.5 billion years ago (key events)
Single-celled organisms altered the evolutionary landscape
Changed atmosphere from negligible to 21% oxygen
Why did the Cambrian period explode? (still marine life)
All major phyla exist by Cambrian (530 million years ago)
Next rapid diversification occurred on land (400 MYA)
Starts with colonization by fungi and plant ancestors
Generated new habits/resources for land animals to evolve
Insects → amphibian/reptiles → mammals → humans
Animal life you are most familiar with are recent additions
The diversity of life on earth is shaped by evolution
The diversity of life on earth is shaped by creation and removal
Speciation events (and thus diversification) can happen quickly
Large extinction events disrupt the progress of diversity
